La differenza tra il numero di tamponi e il numero delle persone testate | Il Post
La strategia dei tamponi: criteri, ritardi, criticità in Italia e all’estero | Valigia Blu
“Tamponi” (“swabs”) refers to “performed tests”: many patients are tested several times (even 5 times). (high confidence | DPC, YT)
Patients who are recovered from COVID-19 are tested at least 3 times: 1 positive and 2 negative. (high confidence | DPC, YT)
“Guariti” (“recovered”) in the official data refers not only to those actually recovered (i.e. who tested negative twice), but to all those discharged from hospital. (high confidence | DPC, IP, IS24O, YT)
The total number of performed tests includes negative test results. (high confidence | DPC)
The total number of performed tests includes those that are pending results. (medium confidence | DPC, PM, RP, RL, TW)
Figures reported by Italian authorities include all tests conducted in all working laboratories of the country. (medium-high confidence | MTP27-02, MTP09-03, MTP03-04)
All Italian regions and laboratories submit testing data on the same basis (i.e. “performed tests”). (medium-high confidence | DPC)
The figures published at a given date attempt to include all tests conducted up to that date, but significant and variable delays are present: both from symptom onset to lab confirmation (\(\Delta T_{symptoms}\)) and from lab confirmation to official database update (\(\Delta T_{lab}\)). (medium-high confidence | ISS)
The median delay between the symptom onset and the date of diagnosis is
For example, in Lombardy \(\Delta T_{symptoms}= 7.3 \text{ days } (1,20)_{95\% \text{CI}}\) and \(\Delta T_{lab} = 3.6 \text{ days } (1,10)_{95\% \text{CI}}\). (high confidence | AXV)
There have been significant changes over time in the ministerial testing protocol. (high confidence | ISS, MTP27-02, MTP09-03, MTP03-04, AXV)
Not all Italian regions follow the ministerial protocol of the central government, therefore there is significant regional heterogeneity in testing practices. (high confidence | IP, IP, IP)
Up to 20-03 we could identify 3 classes of testing practices described by the following pseudocode: consider two patients \(A\) and \(B\) living in the same house in the region \(R \in \{X, Y, Z\}\) such that
If \(A\) and \(B\) live in \(X\):
If \(A\) and \(B\) live in \(Y\):
If \(A\) and \(B\) live in \(Z\):